1. Field of the Invention
The present invention relates to a three-dimensional (3D) radio frequency identification (RFID) tag capable of automatically recognizing orientation, and an environment condition recognition system and method using the 3D RFID tag. More particularly, the present invention relates to a 3D RFID tag, and an environment condition recognition system and method using the 3D RFID tag, capable of recognizing the orientation of a mounted object as well as its own characteristics and the position, and thus presenting a new paradigm in the field of autonomous object sensing, identification, and recognition technology.
2. Description of the Related Art
A typical RFID system is basically composed of a tag (or a card), a reader, and a host computer (or an application). The tag is composed of a radio frequency RF function, a memory, and an antenna (or a power supply), and carries out interfacing using ID information in the memory. Various applications of the RFID system have been developed and put to use according to objects to which ID information in the tag memory and an RF interface are applied, methods of utilizing the same, and a given environment.
RFID is one type of autonomous identification technology using RF communication and performs a function similar to a bar code and a smart card. However, RFID lacks the limits of the bar code which is limited by environmental factors (e.g., rain, snow, fog, contamination, etc.) and the smart card which can only be recognized within an extremely limited range (e.g., several millimeters to tens of millimeters). RFID enables identification even in poor environmental conditions and even when an object is moving at a fast speed ranging from several m/s to tens of m/s. Thus, RFID is widely utilized in industry, for example, in book management systems, livestock management, financial systems, door-to-door delivery systems, electronic toll collection system ETCSs, parking systems, access control systems, physical distribution systems, and so forth.
An RFID tag is composed of an IC chip, an antenna, and an adhesive material, and exchanges predetermined data with an external reader or an interrogator. Thus, the RFID tag is a type of a transponder.
The RFID tag contactlessly transponds data with the reader. It may use inductive coupling, backscattering, surface acoustic wave SAW, etc. in response to high and low frequencies, and may exchange data with the reader in a full duplex FDX, a half duplex HDX, and a sequential SEQ manner using electromagnetic waves. In addition, the transponding method may include amplitude shift keying ASK and frequency shift keying FSK of electromagnetic waves. In addition, the general RFID tag may be classified into two kinds: a disk-shaped antenna coil using a circular air-core coil, and a cylindrical antenna coil consisting of an insulated coating copper wire such as an enamel wire wound around a bar-shaped ferrate core. Outer shapes of the tags correspond to the shapes of the respective antenna coils. Thus, the former type of tag is disc-shaped and the latter type of tag is bar-shaped.
The RFID tag with the disc-shaped antenna coil transponds according to change in magnetic flux in the plane direction of the circular coil, and the RFID tag with the cylindrical antenna coil transponds according to change in magnetic flux in the axial direction.
Conventionally, a low frequency band including 125 kHz, 13.56 MHz, etc. is widely utilized as a frequency band of the RFID tag. However, an ultra high frequency UHF band of 900 MHz has been used recently for managing physical distribution. In particular, the RFID tag is used for managing physical distribution in a large-sized distributor such as Walmart or the U.S. Department of Defense. In such cases, the UHF band and backscattering are usually utilized, and a passive type RF tag, which operates manually in response to external change without a separate built-in battery to generate a necessary current, is recognized as a standard.
Conventional identification methods using RFID include a method of using a tag itself, a method of integrating a tag into a laminated card, a method of using an adhesive medium such as a sticker, and a method of molding a tag by means of injection molding, and so forth.
However, the tag to which the RFID techniques are applied has weak adhesion to an object for obtaining information, cannot be easily attached to and engaged with a product, cannot be recycled, and its RFID circuit is vulnerable to damage caused by external impact.
The RFID tag is composed of an IC chip, an antenna, and an adhesive material. The IC chip is usually based on a film substrate formed of various plastic materials such as polyvinyl chloride PVC, polychlorinated Biphenyl PCB, polyethylene PE, polyamide PA, and polyethylene terephthlate PET, having a thickness of about 100 μm or less, and having an antenna on its upper portion. A conductive wire of the antenna may be mounted on the chip substrate, directly bonded with the IC chip outside the film, or connected in a chip-on-board COB manner
The size of the antenna may increase as a reading range required by the reader increases, may decrease as a radiation power of the reader increases, and may decrease as frequency increases. In this case, when data is exchanged through backscattering using frequency in a band not lower than the UHF band, the degree of backscattering depends on the size and shape of the antenna, geometric conditions, topography, wavelength, and polarization, and efficiency is better for an antenna made of metal.
In summary, in the case of the widely used tag in the frequency band not greater than 13.56 MHz, there are basic limits such as the antenna having to be formed as a coil using inductive coupling, the size of the antenna having to be at least several meters, and the outer housing having to be devoid of metal.
However, the RFID technique using a frequency of at least about 900 MHz, and backscattering, become universal in a field such as physical distribution, so that restrictions on the size of the antenna and the material of the housing are significantly relaxed.
However, electromagnetic waves consist of alternating electric and magnetic fields that are 90 degrees out of phase, and when the alternating magnetic field is applied to a conductive member such as iron, aluminum, or copper, current is induced in a direction so as to generate a magnetic field counter to the alternating magnetic field.
Accordingly, the RFID tag is generally installed as far away from the conductive member as possible.
Therefore, when the RFID tag must be installed close to the conductive member, the RFID tag with the disc-shaped antenna coil is used, a coil side of the RFID tag and a surface of the conductive member are disposed in parallel with each other, and an insulating spacer is interposed therebetween to prevent current induction. Alternatively, a ferrate core or an amorphous magnetic sheet having a high magnetic permeability may be interposed between the coil side and the surface of the conductive member to shield the conductive member and prevent current induction.
Accordingly, effects of the conductive member can be reduced, and communication can be carried out by any of the methods in a direction perpendicular to the coil side, that is, a direction where a magnetic flux distribution is widened by the disc-shaped antenna coil.
The RFID tag with the cylindrical antenna coil can be made significantly smaller than the RFID tag with the disc-shaped antenna coil, and thus has superior adaptability for all uses.
As described above, the magnetic field runs in the axial direction of the antenna coil due to the RFID tag with the cylindrical antenna coil. In communicating with a read/write terminal, better sensitivity can be obtained from a direction of a leading end portion of a core member inserted into the antenna coil.
When this RFID tag is installed on the surface of the conductive member, out of common sense, its axial direction is made to be perpendicular to the surface of the conductive member to facilitate communication. However, it is actually more practical to form an installation groove perpendicular to the surface of the conductive member and install the tag therein.
Further, even when the RFID tag is installed within the installation groove, matching the length of the tag, to communicate with the read/write terminal, communication may be hindered by the surrounding conductive member. Accordingly, in conventional installation with a conductive member, the RFID tag having the disc-shaped antenna coil is used.
However, in the above-described conventional system, information obtained by the RFID only identifies the object and does not reflect its variable physical characteristics (e.g., position, orientation).
That is, the conventional art provides only a unit having a tag mounted at a specific position, or having a function capable of recognizing the position, and a system utilizing this tag to recognize the absolute position of a main body where the moving unit is mounted, and determine position, movement state, and speed of a device. However, the conventional art does not address recognition of the orientation of the object as well as its own characteristics and position.